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Homework Help: Mass & Conversion Problem

  1. Aug 29, 2009 #1
    1. The problem statement, all variables and given/known data

    A piece of pipe has an outer radius of 4.5cm, an inner radius of 2.8cm and length of 36cm

    The density of the pipe is 7.8 g/cm^3

    What is the mass of this pipe? Answer is in unites of kg.

    2. Relevant equations


    Mass= (density)(volume)

    Volume= mass/density

    3. The attempt at a solution

    I subtracted the volume of the hollow inside of the tube from the large radius (2.8+4.5cm) and multiplied that by the density given. Then I converted to kg by dividing by 1000. My answer came up to be appx 40 kg. But I believe I'm wrong.
  2. jcsd
  3. Aug 29, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    The outer radius is given as 4.5 cm. (No need to add 2.8+4.5.)
  4. Aug 29, 2009 #3
    Oh yeah thanks.
    I thought that i had to add the radii because the diagram on the page made it seem as if the outer radius was that of only the thickness of the pipe.
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